Display device and method of driving the same

ABSTRACT

A display device and method of driving the same are disclosed. In one aspect, the display device includes a display panel including a first region and a second region, wherein the first region is configured to display a first image having a first luminance and wherein the second region is configured to display a second image having a second luminance. The display device also includes a panel driver configured to drive the first region at a first frequency and the second region at a second frequency less that the first frequency and a luminance compensator configured to compensate for the difference between the first and second luminances.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2013-0156487 filed on Dec. 16, 2013 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

The described technology generally relates to a display device and amethod of driving the same.

2. Description of the Related Technology

Display devices include a display panel on which images are displayedand a driving unit which drives the display panel. Examples of displaypanels include liquid crystal display (LCD) panels, organiclight-emitting diode (OLED) display panels, plasma display panels(PDPs), and an electrophoretic display (EPD) panels.

Display panels can display either still or moving images. Display panelscan be driven at a frame rate of several frames per second. When anumber of sequential frames display the same image data, a still imageis displayed. Additionally, when sequential frames display differentimage data, a moving image is displayed. The standard display panel isdriven at a frequency of about 60 Hz. Alternatively, display panels canbe driven at frequencies higher than about 60 Hz in order to displayhigh quality moving images. In order to reduce power consumption whendisplaying a still image, display panels can also be driven at lowerfrequencies of about 30 Hz or about 15 Hz. That is, display panels canbe driven at various frequencies depending on whether a still image or amoving image is displayed.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One inventive aspect is a display device which can compensate for thedifference in luminances between a moving-image region and a still-imageregion so as to substantially prevent the boundary between the tworegions from being visible.

Another aspect is a method of driving the display device.

According to at least one embodiment, it is possible to compensate forthe difference in luminances between a moving-image region and astill-image region and thus substantially prevent the boundary betweenthe two regions from being visible.

Another aspect is a display device including a display panel including afirst region driven at a first frequency and a second region driven at asecond frequency that is lower than the first frequency, a panel driverconfigured to drive the display panel and a luminance compensatorconfigured to compensate for a difference between luminance of the firstregion and luminance of the second region.

The luminance compensator is further configured to correct one or moredata voltages applied to the first region to correspond to one or moredata voltages that are discharged in the second region.

The luminance compensator is further configured to lower the datavoltages applied to the first region such that an average of the datavoltages applied to the first region becomes substantially identical toan average of the data voltages applied to the second region.

The display device may further include a memory configured to store aplurality of lookup tables (LUTs) in which correction data for the firstregion is stored in the form of a matrix.

The display device may further include a luminance measurement unitconfigured to measure luminance of the display panel and output aluminance signal corresponding to the measured luminance to the timingcontrol unit, the luminance compensator is further configured to controlthe first region and the second region to have substantially the sameluminance according to the luminance signal.

The display device may further include a light source unit configured toprovide light to the display panel and a light source driving unitconfigured to control the light source unit, wherein the luminancecompensator is further configured to provide a light source controlsignal having a waveform that is symmetrical with the waveform of theluminance signal to the light source driving unit and the light sourcedriving unit is further configured to drive the light source unitaccording to the light source control signal.

The display device may further include an image controller configured tocompare image data of a current frame and image data of a previous frameand thus to set the first region and the second region in the displaypanel.

The first region includes a moving-image display region and the secondregion includes a still-image display region.

The first frequency is about 60 Hz and the second frequency is about 20Hz.

Another aspect is a display device including a plurality of pixelscomprising a first pixel group and a second pixel group, wherein thefirst pixel group is configured to display a first image having a firstluminance and wherein the second pixel group is configured to display asecond image having a second luminance, a plurality of scan lineselectrically connected to the pixels, a plurality of data lines crossingthe scan lines and electrically connected to the pixels, a scan driverconfigured to respectively apply a plurality of scan signals to the scanlines and drive the first pixel group at a first frequency and thesecond pixel group at a second frequency, a data driver configured torespectively apply a plurality of data voltages to the data lines and aluminance compensator configured to compensate for the differencebetween the first and second luminances.

The luminance compensator is further configured to respectively applyfirst and second data voltages to the first and second pixel groups andwherein the luminance compensator is further configured to lower one ormore of the first data voltages over a single frame period such that theaverage of the first data voltages is substantially the same as theaverage of the second data voltages applied to the second pixel group.

The display device further includes a light source configured to providelight to the pixels, wherein the luminance compensator is furtherconfigured to increase luminance of the light source based at least inpart on a decrease in the second luminance.

at least one of the pixels in the first pixel group is configured todisplay a moving-image and wherein at least one of the pixels in thesecond pixel group is configured to display a still-image.

The first frequency is about 60 Hz and the second frequency is about 20Hz.

The display device further comprises an image controller configured to:receive present frame image data and previous frame image data, comparethe present frame image data to the previous frame image data and setthe first pixel group and the second pixel group based at least in parton the comparison.

Another aspect is a method of driving a display device including adisplay panel including a first region and a second region, the methodcomprising displaying a first image having a first luminance in thefirst region, displaying a second image having a second luminance in thesecond region, driving the first region at a first frequency and thesecond region at a second frequency, compensating image data for thedifference between the first and second luminances, converting thecompensated image data into data voltages and applying the data voltagesto the display panel.

The compensating comprises lowering one or more of the first datavoltages over a single frame period such that the average of the firstdata voltages applied is substantially the same as the average of thesecond data voltages.

The display device further comprises a light source, wherein the methodfurther comprises the light source providing light to the display panel,and wherein the compensating comprises increasing luminance of the lightsource based at least in part on a decrease in the luminance of thesecond region.

The first frequency is about 60 Hz and the second frequency is about 20Hz.

The first region includes a moving-image display region and the secondregion includes a still-image display region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a display device according to anembodiment.

FIG. 2 is a diagram illustrating a scan signal according to anembodiment.

FIG. 3 is a block diagram of the timing control unit illustrated in FIG.1.

FIG. 4 is a graph showing variations in the luminance of a first region.

FIG. 5 is a graph showing variations in the luminance of a secondregion.

FIG. 6 is a diagram illustrating the compensation of the luminance ofthe first region according to the variation of the luminance of thesecond region.

FIG. 7 is a graph showing the charge rate of each pixel of a displaypanel before luminance compensation.

FIG. 8 is a diagram illustrating the charge rate of each pixel of adisplay panel after luminance compensation.

FIG. 9 is a block diagram of a display device according to anotherembodiment.

FIG. 10 is a block diagram of the timing control unit illustrated inFIG. 9.

FIG. 11 is a block diagram of the image controller illustrated in FIG.10.

FIG. 12 is a block diagram of a display device according to anotherembodiment.

FIG. 13 is a block diagram of the timing control unit illustrated inFIG. 12.

FIG. 14 is a waveform diagram illustrating a luminance signal and alight source driving signal.

FIG. 15 is a block diagram of a display device according to anotherembodiment.

FIG. 16 is a flowchart illustrating a method of driving a display deviceaccording to an embodiment.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Low-frequency driving of display panels can result in severe dischargeof data voltages stored in each pixel. This can cause severe luminancefluctuations because of the relatively long frame duration. That is,data voltages are discharged for a longer time period when displayingstill-images driven at low frequencies than when displayingmoving-images driven at high frequencies. Thus, the luminance of adisplay device varies between still and moving-image regions, which canresult in a visible boundary between the regions.

The aspects and features of the described technology and methods forachieving the aspects and features will be apparent by referring to theembodiments to be described in detail with reference to the accompanyingdrawings. However, the described technology is not limited to theembodiments disclosed hereinafter, but can be implemented in diverseforms. The matters defined in the description, such as the detailedconstruction and elements of the described technology, are nothing butspecific details provided to assist those of ordinary skill in the artin a comprehensive understanding of the described technology and thedescribed technology is only defined within the scope of the appendedclaims.

The term “on” that is used to designate that an element is on anotherelement or located on a different layer or a layer includes both when anelement is located directly on another element or a layer and when anelement is located on another element with another layer or stillanother element interposed therebetween. In the entire description, thesame drawing reference numerals are used for the same elements acrossvarious figures.

Although the terms “first”, “second”, and so forth are used to describevarious constituent elements, such constituent elements are not limitedby these terms. These terms are used only to differentiate a constituentelement from other constituent elements. Accordingly, in the followingdescription, a first constituent element may termed be a secondconstituent element without departing from the scope of the describedtechnology.

Hereinafter, embodiments will be described with reference to theattached drawings.

FIG. 1 is a block diagram of a display device according to anembodiment. FIG. 2 is a diagram illustrating a scan signal according toan embodiment.

Referring to FIG. 1, a display device 10 includes a display panel 110, apanel driver PD, and a luminance compensator 141.

Various types of display panels may be employed as the display panel 110depending on how the display device 10 displays an image. As an example,the display panel 110 may be, but is not limited to, one of a liquidcrystal display (LCD) panel, an organic light-emitting diode (OLED)panel, a plasma display panel (PDP), or an electrophoretic display (EPD)panel.

The display panel 110 includes a plurality of scan lines (SL1, SL2, . .. , SLn), a plurality of data lines (DL1, DL2, . . . , DLm), and aplurality of pixels PX. The scan lines (SL1, SL2, . . . , SLn) extend inone direction and are substantially parallel to one another. The scanlines (SL1, SL2, . . . , SLn) include first through n-th scan lines SL1through SLn. A plurality of first through n-th scan signals S1 throughSn are respectively applied to the first through n-th scan lines SL1through SLn. The data lines (DL1, DL2, . . . , DLm) include firstthrough m-th data lines DL1 through DLm. The data lines DL1 to DLmintersect the scan lines SL1 to SLn. The data lines DL1 to DLm extend ina different direction from the scan lines SL1 through SLn and aresubstantially parallel to one another. A plurality of first through m-thdata voltages D1 through Dm are respectively applied to the firstthrough m-th data lines DL1 through DLm.

The pixels PX are arranged in a matrix, but the described technology isnot limited to this. The pixels PX are respectively connected to thescan lines SL1 to SLn and the data lines DL1 to DLm. The pixels PXrespectively receive the data voltages D1 to Dm from the data lines DL1to DLm in response to the receiving the scan signals S1 to Sn from thescan lines SL1 to SLn. Each of the scan signals SL1 to SLn includes ascan-on signal Son and a scan-off signal Soff. In response to receivingthe scan-on signal Son, the pixels PX respectively receive the datavoltages D1 to Dm from the data lines DL1 to DLm. Similarly, in responseto receiving the scan-off signal Soff, the pixels PX do not receive thedata voltages D1 to Dm.

Each of the pixels PX receives one of the data voltages D1 to Dm andemits light with a grayscale level corresponding to the received datavoltage. The display panel 110 includes a first region 111 which isdriven at a first frequency and a second region 112 which is driven at asecond frequency that is less than the first frequency. In the firstregion 111, the first through (j−1)-th scan lines SL1 through SLj-1respectively receive the first through (j−1)-th scan signals S1 throughSj-1, which have the first frequency. As a result, the first throughm-th data voltages D1 through Dm are received by the correspondingpixels PX. In the second region 112, the j-th through n-th scan linesSLj through SLn respectively receive the j-th through n-th scan signalsSj through Sn, which have the second frequency. In some embodiments, thefirst frequency and the second frequency are about 60 Hz and about 20Hz, respectively, however the described technology is not limitedthereto. In other embodiments, the first frequency is greater than about60 Hz and the second frequency is less than about 20 Hz.

The first region 111 includes a moving-image display region and thesecond region 112 includes a still-image display region. That is, atleast part of the first region 111 is the moving-image display region.The moving-image display region is part of the display panel 110 wheredifferent data voltages are applied in a current frame and a subsequentframe. The still-image display region is part of the display panel 110where the same data voltages are applied in the current frame and thesubsequent frame. The first region 111 in which a moving image isdisplayed is driven at a frequency of about 60 Hz and the second region112 in which a still image is displayed is driven at a frequency ofabout 20 Hz. The frequency of about 60 Hz corresponds to a frame rate ofabout 60 frames per second and the frequency of about 20 Hz correspondsto a frame rate of about 20 frames per second. Accordingly, in responseto the display panel 110 being driven at a frequency of about 20 Hz, thepower consumption of the display panel 110 is reduced to about ⅓compared to when the display panel 110 is driven at a frequency of about60 Hz. That is, the power consumption of the display panel 110 isreduced by driving the display panel 110 at a low frequency during astill-image display period that does not require high-speed driving.

Due to the difference between the frequencies of the data voltagesapplied to the first and second regions 111 and 112, the amount ofcharge discharged by each pixel differs in the first and second regions111 and 112. As a result, the pixels in each of the first and secondregions 111 and 112 may have different luminance levels. Accordingly,the boundary PB between the first region 111 and the second region 112may be visible. The luminance compensator 141 of the display device 10compensates for the difference between the luminances of the first andsecond regions 111 and 112 and may prevents the boundary PB between thefirst and second regions 111 and 112 from being visible.

The panel driver PD includes a data driving unit or data driver 120, ascan driving unit or scan driver 130, and a timing control unit ortiming controller 140. The panel driver PD can be provided separatelyfrom the display panel 110 or can be at least partially incorporatedinto the display panel 110.

The data driving unit 120 generates the data voltages D1 to Dm andrespectively applies the data voltages D1 to Dm to the data lines DL1through DLm. More specifically, the data driving unit 120 receivescorrected image data DATA′ and generates the data voltages D1 to Dmbased on the corrected image data DATA′. The corrected image data DATA′is image data obtained by correcting image data DATA so as to lower thenumber of data voltages corresponding to the first region 111 tocompensate for the difference between the luminances of the first andsecond regions 111 and 112.

The scan driving unit 130 respectively applies the scan signals S1 to Snto the scan lines SL1 to SLn. The scan signals S1 to Sn can be dividedinto a first group G1 including one or more scan signals having thefirst frequency and a second group G2 including one or more scan signalshaving the second frequency. In a non-limiting example, the first groupG1 includes the first through (j−1)-th scan signals S1 through Sj-1 andthe second group G2 includes the j-th through n-th scan signals Sjthrough Sn, as illustrated in FIG. 2. The first frequency is about 60 Hzand the second frequency is about 20 Hz. That is, the first group G1 isscanned every 1/60 seconds to receive data voltages and the second groupG2 is scanned every 1/20 seconds to receive data voltages. The scansignals included in the first group G1 are applied to the scan linesincluded in the first region 111, i.e., the first through (j−1)-th scanlines SL1 through SLj-1. The scan signals included in the second groupG2 are applied to the scan lines included in the second region 112,i.e., the j-th through n-th scan lines SLj through SLn. The scan drivingunit 130 controls one of the first and second groups G1 and G2 to havedifferent frequencies according to a scan control signal SCS. In someembodiments, the scan driving unit 130 includes a plurality of scandrivers (not illustrated) which provide different scan signals to thedifferent groups. In some embodiments, the scan driving unit 130includes a first scan driver (not illustrated) applying a scan signalwith a first frequency to the first through (j−1)-th scan lines SL1through SLj-1 in the first region 111 and a second scan driver (notillustrated) applying a scan signal with a second frequency to the j-ththrough n-th scan lines SLj through SLn in the second region 112.

The timing control unit 140 receives the image data DATA and a controlsignal TCS and generates the scan control signal SCS, a data controlsignal DCS, and the corrected image data DATA′ based on the image dataDATA and the control signal TCS. The scan control signal SCS is providedto the scan driving unit 130 so as to control the scan driving unit 130.The scan control signal SCS can include a vertical synchronizationsignal. The data control signal DCS is provided to the data driving unit120 so as to control the data driving unit 120. The data control signalDCS can include a horizontal synchronization signal. The corrected imagedata DATA′ is provided to the data driving unit 120. In the FIG. 1embodiment, the timing control unit 140 includes the luminancecompensator 141, but the described technology is not limited to this.That is, the luminance compensator 141 can be provided separately fromthe timing control unit 140. The display device 10 will hereinafter bedescribed in further detail with reference to FIGS. 3 to 8.

Referring to FIG. 3, the timing control unit 140 includes the luminancecompensator 141, a data control signal generator 142, a scan controlsignal generator 143, and a memory 144.

The luminance compensator 141 receives the image data DATA from anexternal source, generates the corrected image data DATA′ by correctingthe image data DATA such that the difference between the luminance ofthe first region 111 and the luminance of the second region 112 iscompensated for, and outputs the corrected image data DATA′ to the datadriving unit 120. More specifically, the luminance compensator 141compensates for the difference between the luminances of the first andsecond regions 111 and 112 by lowering the data voltages applied to thefirst region 111 so as to correspond to the average of the data voltagesthat are applied to and discharged from the second region 112 over asingle frame period.

Referring to FIGS. 4 to 8, the first region 111 is driven at a highfrequency of about 60 Hz, which corresponds to a frame length of about1/60 seconds, and the second region 112 is driven at a low frequency ofabout 20 Hz, which corresponds to a frame length of about 3/60 seconds.As illustrated in FIG. 4, in response to the thin-film transistors(TFTs) of the pixels in the first region 111 being turned on by the scansignals S1 to Sj-1, each of the pixels in the first region 111 ischarged with a data voltage and the luminance L1 of the pixels in thefirst region 111 gradually increases to a maximum level max1. Inresponse to the TFTs of the pixels in the first region 111 being turnedoff, the data voltage stored in each of the pixels in the first region111 discharges until each of the pixels in the first region 111recharged with a data voltage for a subsequent frame. The luminance L1reaches a minimum level min1 just prior to being recharged.

As illustrated in FIG. 5, in response to the TFTs of the pixels in thesecond region 112 being turned on by the scan signals Sj through Sn,each of the pixels in the second region 112 is charged with a datavoltage and the luminance L2 of the pixels in the second region 112gradually increases to a maximum level max2. In response to the TFTs ofthe pixels in the second region 112 being turned off, the data voltagestored in each of the pixels in the second region 112 discharges untileach of the pixels in the second region 112 is recharged. The luminanceL2 reaches a minimum level min2 just prior to being recharged.

Since the length of each frame is longer in the second region 112 thanin the first region 112, the amount by which the data voltage isdischarged and the variation in the luminance is greater in the secondregion 112 than in the first region 111. That is, the discharge of thestored data voltages continues for the pixels in the second region 112even when the pixels in the first region 111 are recharged with a datavoltage for a subsequent frame. Accordingly, as illustrated in FIG. 6,the data voltage averages avg1 in the first region 111 are initiallysubstantially identical to the average luminance avg2-1. However, thedata voltage averages avg1 gradually grow apart from the averageluminance avg2-1, avg2-2, avg2-3 in the second region 112. Due to thedifference between the luminances of the first and second regions 111and 112, the boundary PB between the first region 111 and the secondregion 112 becomes visible. The luminance compensator 141 compensatesfor data voltage averages avg1, avg1′ and avg″ in the first region 111so as to respectively correspond to data voltage averages avg2-1, avg2-2and avg2-3 in the second region 112. That is, the luminance compensator141 lowers the luminance of the first region 111 to correspond to thedecrease in luminance of the second region 112.

Referring to the corrected image data DATA′ illustrated in FIG. 7, thedata voltage average avg1′ for a second frame in the first region 111 issubstantially the same as the data voltage average avg2-2 in the secondregion 112. Similarly, the data voltage average avg1″ for a third framein the first region 111 is substantially the same as the data voltageaverage avg2-3 in the second region 112. The corrected image data DATA′,which is provided by the luminance compensator 141, has substantiallythe same data voltage average in both the first region 111 and thesecond region 112 for a given frame. Therefore, as illustrated in FIG.8, the boundary between the first region 111 and the second region 112is not visible due to the compensation of luminance by the luminancecompensator 141.

Referring back to FIG. 3, the memory 144 includes a plurality of lookuptables (LUTs) in which corrected image data for the first region 111 isstored in the form of matrix. The luminance compensator 141 may readsthe corresponding LUT from the memory 144. More specifically, theluminance compensator 141 provides a selection signal SC to the memory144. In response to the selection signal SC, the memory 144 providescorrection image data LUTD from a LUT corresponding to the selectionsignal SC to the luminance compensator 141. The luminance compensator141 corrects the image data DATA based on the correction image dataLUTD, thereby obtaining the corrected image data DATA′. The luminancecompensator 141 outputs the corrected image data DATA′ to the datadriving unit 120.

The data control signal generator 142 and the scan control signalgenerator receive the control signal TCS from an external source. Thecontrol signal TCS may include a vertical synchronization signal Vsync,a horizontal synchronization signal Hsync, a data enable signal DE, anda clock signal CLK.

The data control signal generator 142 generates the data control signalDCS, which is for controlling the data driving unit 120, in response tothe receipt of the control signal TCS. The data control signal generator142 outputs the data control signal DCS to the data driving unit 120. Insome embodiments, the data control signal DCS includes a source startpulse SSP, a source sampling clock SSC, a source output enable signalSOE, and a polarity signal POL.

The scan control signal generator 143 generates the scan control signalSCS, which is for controlling the scan driving unit 130, in response tothe receipt of the control signal TCS. The scan control signal generator143 outputs the scan control signal SCS to the scan driving unit 130.The scan control signal SCS controls the scan driving unit 130 tosequentially generate a plurality of scan signals. The scan signals aredivided into a first group G1 and a second group G2. The scan controlsignal SCS controls the scan signals included in the first group G1 andthe scan signals included in the second group G2 to have differentfrequencies.

A display device according to another embodiment will hereinafter bedescribed with reference to FIGS. 9 to 11. FIG. 9 is a block diagram ofa display device according to another embodiment. FIG. 10 is a blockdiagram of the timing control unit illustrated in FIG. 10. FIG. 11 is ablock diagram of the image controller illustrated in FIG. 10.

Referring to FIGS. 9 to 11, a display device 20, in contrast to thedisplay device 10 of FIGS. 1 to 8, further includes an image controller245. The image controller 245 is included in a timing control unit 240,but the described technology is not limited to this. That is, the imagecontroller 245 may be provided separately from the timing control unit240.

The image controller 245 includes a comparator 246 and a second memory247. The comparator 246 receives image data DATA for a current frame anda control signal TCS. The comparator 246 outputs the image data DATA tothe second memory 247 and reads image data P_DATA of a previous framefrom the second memory 247. The second memory 247 stores the image dataDATA. The comparator 246 sets a first region 211 and a second region 212in the display panel 210 by comparing the image data DATA to theprevious image data P_DATA. The first region 211 includes a moving-imagedisplay region and the second region 212 includes a still-image displayregion. A region in the display panel 210 where there are no changes tothe values of the image data is set as the second region 212, but thedescribed technology is not limited to this. The comparator 246 outputsimage data DATA′ indicating the boundaries of the first region 211 andthe second region 212 and a control signal TCS′ to the luminancecompensator 241, a data control signal generator 242, and a scan controlsignal generator 243. The luminance compensator 241 compensates for theluminance of the first region 211. The scan control signal generator 243controls scan signals to have different frequencies to be applied to thefirst region 211 and the second region 212.

The display device 20 sets the first region 211 and the second region212 in the display panel 210 by comparing the image data DATA of thecurrent frame and the image data P_DATA of the previous frame. Thedisplay device 20 compensates for the luminance of the first region 211so as to prevent the boundary between the first and second regions 211and 212 from being visible.

The other elements of the display device 20 are substantially identicalto their respective counterparts of the display device 10 of FIGS. 1 to8, and thus, detailed descriptions thereof will be omitted.

A display device according to another embodiment will hereinafter bedescribed with reference to FIGS. 12 to 14. FIG. 12 is a block diagramof a display device according to another embodiment. FIG. 13 is a blockdiagram of the timing control unit illustrated in FIG. 12. FIG. 14 is awaveform diagram illustrating a luminance signal and a light sourcedriving signal.

Referring to FIG. 12, a display device 30, in contrast to the displaydevice 10 of FIGS. 1 to 8, further includes a luminance measurement unit350, a light source driving unit or light source driver 360, and a lightsource unit or light source 370. In some embodiments, the display device30 is an LCD including a backlight unit, however the describedtechnology is not limited thereto.

The luminance measurement unit 350 measures the luminance of a displaypanel 310. In some embodiments, the luminance measurement unit 350 is aphoto sensor, however, the described technology is not limited thereto.The luminance measurement unit 350 converts the variation in theluminance of the display panel 310 over a single frame period into aluminance signal PL and outputs the luminance signal PL to the timingcontrol unit 340. The luminance compensator 341 of the timing controlunit 340 receives the luminance signal PL and controls data signalsapplied to a first region 311 and a second region 312 of the displaypanel 310 based on the luminance signal PL such that the first region311 and the second region 312 may have the same luminance. In responseto the receipt of the luminance signal PL, the luminance compensator 341outputs a light source control signal LCS to the light source drivingunit 360.

The light source driving unit 360 controls and drives the light sourceunit 370. The light source unit 370 provides light to the display panel310, and in some embodiments, is a backlight unit. In some embodiments,the light source unit 370 includes a plurality of light sources and thelight sources respectively correspond to a plurality of pixels PX of thedisplay panel 310. The luminance of the pixels PX are adjusted by theamount of light emitted from the light sources.

The light source driving unit 360 drives the light source unit 370according to the light source control signal LCS. Referring to FIG. 14,the waveforms of the luminance signal and the light source controlsignal LCS are symmetrical with respect to each other. That is, as theluminance of the luminance signal PL increases, the luminance of thelight source unit 370 decreases. As the luminance of the luminancesignal PL decreases, the luminance of the light source unit 370increases. The luminance signal PL represents the luminance of thesecond region 312, which decreases upon the discharge of data voltagesin the second region 312. The luminance compensator 341 outputs thelight source control signal LCS so as to increase the luminance of partof the light source unit 370 corresponding to the second region 312 bythe amount corresponding to a decrease in the luminance of the secondregion 312, and thus controls the boundary between the first region 311and the second region 312 so as to not be visible.

The other elements of the display device 30 are substantially identicalto their respective counterparts of the display device 10 of FIGS. 1 to8, and thus, detailed descriptions thereof will be omitted.

FIG. 15 is a block diagram of a display device according to anotherembodiment.

Referring to FIG. 15, a display device 40 includes a plurality of scanlines (SL1, SL2, . . . , SLn), a plurality of pixels PX, a plurality ofdata lines (D1, D2, . . . , DLm), a data driving unit or data driver420, a scan driving unit or scan driver 430, a timing control unit ortiming controller 440 and a luminance compensator 441.

The scan lines (SL1, SL2, . . . , SLn) extend in one direction and aresubstantially parallel to one another. The scan lines (SL1, SL2, . . . ,SLn) include first through n-th scan lines SL1 through SLn. A pluralityof first through n-th scan signals S1 through Sn are respectivelyapplied to the first through n-th scan lines SL1 through SLn.

The data lines (DL1, DL2, . . . , DLm) include first through m-th datalines DL1 through DLm. The data lines DL1 to DLm intersect the scanlines SL1 to SLn. The data lines DL1 to DLm extend in a differentdirection from the scan lines SL1 to SLn and are substantially parallelto one another. A plurality of first through m-th data voltages D1through Dm are respectively applied to the first through m-th data linesDL1 through DLm.

The pixels PX are arranged in a matrix, but the described technology isnot limited to this. The pixels PX are respectively connected to thescan lines SL1 to SLn and the data lines DL1 to DLm. The pixels PXrespectively receive the data voltages D1 to Dm from the first datalines DL1 to DLm in response to receiving the scan signals S1 to Sn fromthe scan lines SL1 to SLn. Each of the scan signals SL1 to SLn includesa scan-on signal Son and a scan-off signal Soff. In response to thereceipt of the scan-on signal Son, the pixels PX respectively receivethe data voltages D1 to Dm from the data lines DL1 to DLm.Alternatively, in response to the receipt of the scan-off signal Soff,the pixels PX do not receive the data voltages D1 to Dm. Each of thepixels PX receives a corresponding data voltage D1 to Dm and emits lightwith a corresponding a grayscale level.

The data driving unit 420 respectively provides the data voltages D1 toDm to the data lines DL1 through DLm.

The scan driving unit 430 respectively provides the scan signals S1 toSn to the scan lines SL1 through SLn.

The scan lines SL1 to SLn include a first scan line group GL1 to whichscan signals having a first frequency are applied and a seconds scanline group GL2 to which scan signals having a second frequency areapplied, wherein the second frequency is different from the firstfrequency. The pixels PX include a first pixel group 411 connected tothe first scan line group GL1 and a second pixel group 412 connected tothe second scan line group GL2. The first frequency and the secondfrequency may be, but are not limited to, about 60 Hz and about 20 Hz,respectively. That is, the pixels included in the first pixel group 411are driven at a high frequency of about 60 Hz or greater and the pixelsincluded in the second pixel group 412 are driven at a low frequency ofabout 20 Hz or less. The pixels included in the first pixel group 411display a moving image and the pixels included in the second pixel group412 display a still image. That is, the power consumption of the displaydevice 40 can be reduced by driving the first pixel group 411, whichdisplays a moving image, at a high frequency and driving the secondpixel group 412, which displays a still image, at a low frequency.

Due to the difference between the frequencies applied to the first andsecond pixel groups 411 and 412, the first and second pixel groups 411and 412 may differ from each other in terms of the amount of dischargefrom a data voltage charged in each pixel. As a result, the pixel groupsmay have different luminance levels. Accordingly, a boundary PB betweenthe first and second pixel groups 411 and 412 may become visible. Theluminance compensator 441 of the display device 40 compensates for thedifference between the luminance of the first and second pixel groups411 and 412. The luminance compensator 441 lowers the average of datavoltages applied to the first pixel group 411 over a single frame periodsuch that the first pixel group 411 has substantially the same datavoltage average as the second pixel group 412 over the single frameperiod. Accordingly, the boundary PB between the first pixel group 411and the second pixel group 412 can be prevented from being visible.

In some embodiments, the display device 40 also includes a light sourceunit or light source 470 which provides a source of light to the pixelsPX. The luminance compensator 441 increases the luminance of part of thelight source unit 470 corresponding to the second pixel group 412 by anamount corresponding to the decrease in the luminance of the secondpixel group 412, and thus prevents the boundary PB between the first andsecond pixel groups 411 and 412 from being visible.

In some embodiments, the display device 40 also includes an imagecontroller 450 which sets the boundaries of the first pixel group 441and the second pixel group 442 by comparing image data DATA of a currentframe and image data P_DATA of a previous frame. That is, the firstpixel group 441, which displays moving images, and the second pixelgroup 442, which displays a still image, may be set by the imagecontroller 450. In this example, the boundary PB between the first andsecond pixel groups 411 and 412 can be prevented from being visible bycompensating for the difference between the luminances of the first andsecond pixel groups 411 and 412.

The other elements of the display device 40 are substantially identicalto their respective counterparts of the display device 10 of FIGS. 1 to8, and thus, detailed descriptions thereof will be omitted.

A method of driving a display device, according to an embodiment willhereinafter be described.

FIG. 16 is a flowchart illustrating a method of driving a displaydevice, according to an embodiment.

Referring to FIG. 16, the method includes correcting image data (S110),converting the corrected image data into a data voltage (S120), andapplying the data voltage (S130). The method will hereinafter bedescribed in further detail with reference to FIG. 1.

First, image data is corrected (S110).

More specifically, image data DATA is corrected by the luminancecompensator 141 of the timing control unit 140. That is, the luminancecompensator 141 corrects the image data DATA to compensate for thedifference between the luminances of the first region 111, which isdriven at a first frequency, and the second region 112, which is drivenat a second frequency that is different from the first frequency. Thefirst frequency is a high frequency and the second frequency is a lowfrequency. In some embodiments, the first frequency and the secondfrequency may be, but are not limited to, about 60 Hz and about 20 Hz,respectively.

The first region 111 is one part of the display panel 110 to which ascan signal with the first frequency is applied and the second region112 is another part of the display panel 110 to which a scan signal withthe second frequency is applied. The first region 111 includes amoving-image display region and the second region 112 includes astill-image display region. Due to the difference between thefrequencies applied to the first and second regions 111 and 112, thefirst and second regions 111 and 112 differ from each other in terms ofthe amount of discharge from a data voltage charged in each pixel. As aresult, the first and second regions 111 and 112 have differentluminance levels. Accordingly, the boundary PB between the first andsecond regions 111 and 112 may become visible. The luminance compensator141 compensates for the difference between the luminances of the firstand second regions 111 and 112. More specifically, the luminancecompensator 141 lowers the average of data voltages applied to the firstregion 111 over a single frame period such that the first region 111 hassubstantially the same data voltage average as the second region 112 forthe single frame period. Accordingly, the boundary PB between the firstregion 111 and the second region 112 can be prevented from beingvisible.

The memory 144 includes a plurality of LUTs in which correction imagedata LUTD for the first region 111 is stored in the form of a matrix.The luminance compensator 141 reads an LUT corresponding to the imagedata DATA from the memory 144. More specifically, the luminancecompensator 141 provides a selection signal SC to the memory 144 and inresponse to the selection signal SC, the memory 144 provides correctionimage data LUTD from an LUT corresponding to the selection signal SC tothe luminance compensator 141. The luminance compensator 141 correctsthe image data DATA based on the correction image data LUTD, therebyobtaining the corrected image data DATA′. The luminance compensator 141outputs the corrected image data DATA′ to the data driving unit 120.

Next, the corrected image data is converted into a data voltage (S120).

More specifically, the data driving unit 120 receives the correctedimage data DATA′ and the data control signal DCS from the timing controlunit 140. The data driving unit 120 also receives a gamma voltage from agamma voltage generation unit (not illustrated). The data driving unit120 converts the corrected image data DATA′, which is digital data, intoan analog data voltage by using the gamma voltage. That is, the datadriving unit 120 converts the corrected image data DATA′ into a datavoltage by using, for example, linear interpolation.

The data voltage obtained from the corrected image data is applied to adisplay panel (S130).

More specifically, the data driving unit 120 includes a buffer (notillustrated). The data voltage obtained from the corrected image dataDATA′ is applied to the buffer. The buffer buffers the data voltageobtained from the corrected image data DATA′ and outputs the buffereddata voltage to each data line of the display panel 110.

The other steps or processes of the method of FIG. 16 are substantiallyidentical to the descriptions of the corresponding elements of thedisplay device 10 of FIGS. 1 to 8, and thus, detailed descriptionsthereof will be omitted.

Although embodiments have been described with reference to a number ofillustrative embodiments, it should be understood that numerous othermodifications and embodiments can be devised by those skilled in the artthat will fall within the spirit and scope of the invention. Moreparticularly, various modifications are possible to the component partsand/or arrangements within the scope of the invention. In addition tovariations and modifications in the component parts and/or arrangements,alternative uses will also be apparent to those skilled in the art.

What is claimed is:
 1. A display device, comprising: a display panelcomprising a first region and a second region, wherein the first regionis configured to display a first image having a first luminance andwherein the second region is configured to display a second image havinga second luminance; a panel driver configured to drive the first regionat a first frequency and the second region at a second frequency lessthat the first frequency; and a luminance compensator configured tocompensate for the difference between the first and second luminances.2. The display device of claim 1, wherein the panel driver is furtherconfigured to respectively apply first and second data voltages to thefirst and second regions, wherein the second data voltages areconfigured to be discharged over time, and wherein the luminancecompensator is further configured to correct the first data voltages soas to correspond to the discharged second data voltages.
 3. The displaydevice of claim 2, wherein the luminance compensator is furtherconfigured to reduce the first data voltages such that the average ofthe first data voltages is substantially the same as the average of thesecond data voltages.
 4. The display device of claim 2, furthercomprising a memory storing a plurality of lookup tables (LUTs)comprising correction data for the first region.
 5. The display deviceof claim 1, further comprising a luminance measurement unit configuredto measure luminance of the display panel and output a luminance signalcorresponding to the measured luminance to the luminance compensator,wherein the luminance compensator is further configured to compensatefor the difference in the luminances based at least in part on theluminance signal.
 6. The display device of claim 5, further comprising:a light source configured to provide light to the display panel; and alight source driver configured to control the light source, wherein theluminance compensator is further configured to provide a light sourcecontrol signal to the light source driver, wherein the waveform of thelight source control signal is substantially symmetrical with respect tothe waveform of the luminance signal, and wherein the light sourcedriver is further configured to drive the light source based at least inpart on the light source control signal.
 7. The display device of claim1, further comprising an image controller configured to: receive presentframe image data and previous frame image data; compare the presentframe image data to the previous frame image data; and set the firstregion and the second region in the display panel based at least in parton the comparison.
 8. The display device of claim 1, wherein the firstimage is a moving-image the second image is a still-image.
 9. Thedisplay device of claim 1, wherein the first frequency is about 60 Hzand the second frequency is about 20 Hz.
 10. A display device,comprising: a plurality of pixels comprising a first pixel group and asecond pixel group, wherein the first pixel group is configured todisplay a first image having a first luminance and wherein the secondpixel group is configured to display a second image having a secondluminance; a plurality of scan lines electrically connected to thepixels; a plurality of data lines crossing the scan lines andelectrically connected to the pixels; a scan driver configured torespectively apply a plurality of scan signals to the scan lines anddrive the first pixel group at a first frequency and the second pixelgroup at a second frequency; a data driver configured to respectivelyapply a plurality of data voltages to the data lines; and a luminancecompensator configured to compensate for the difference between thefirst and second luminances.
 11. The display device of claim 10, whereinthe data driver is further configured to respectively apply first andsecond data voltages to the first and second pixel groups and whereinthe luminance compensator is further configured to lower one or more ofthe first data voltages over a single frame period such that the averageof the first data voltages is substantially the same as the average ofthe second data voltages applied to the second pixel group.
 12. Thedisplay device of claim 10, further comprising a light source configuredto provide light to the pixels, wherein the luminance compensator isfurther configured to increase luminance of the light source based atleast in part on a decrease in the second luminance.
 13. The displaydevice of claim 10, wherein at least one of the pixels in the firstpixel group is configured to display a moving-image and wherein at leastone of the pixels in the second pixel group is configured to display astill-image.
 14. The display device of claim 10, wherein the firstfrequency is about 60 Hz and the second frequency is about 20 Hz. 15.The display device of claim 10, further comprising an image controllerconfigured to: receive present frame image data and previous frame imagedata; compare the present frame image data to the previous frame imagedata; and set the first pixel group and the second pixel group based atleast in part on the comparison.
 16. A method of driving a displaydevice comprising a display panel including a first region and a secondregion, the method comprising: displaying a first image having a firstluminance in the first region; displaying a second image having a secondluminance in the second region; driving the first region at a firstfrequency and the second region at a second frequency; compensatingimage data for the difference between the first and second luminances;converting the compensated image data into data voltages; and applyingthe data voltages to the display panel.
 17. The method of claim 16,wherein the compensating comprises lowering one or more of the firstdata voltages over a single frame period such that the average of thefirst data voltages applied is substantially the same as the average ofthe second data voltages.
 18. The method of claim 16, wherein thedisplay device further comprises a light source, wherein the methodfurther comprises the light source providing light to the display panel,and wherein the compensating comprises increasing luminance of the lightsource based at least in part on a decrease in the luminance of thesecond region.
 19. The method of claim 16, wherein the first frequencyis about 60 Hz and the second frequency is about 20 Hz.
 20. The methodof claim 16, wherein the first image is a moving-image and wherein thesecond image is a still-image.